The invention relates in general to offshore drilling platforms. More particularly, it relates to a new and useful conductor guide arrangement for positioning a plurality of tubular conductors used in an offshore drilling platform which conductors extend upwardly through a pile of the platform jacket.
The drilling of wells at offshore locations using offshore platforms is accomplished through large diameter steel pipes, called conductors, which are driven into the soil at the sea bed through guides connected to a jacket and deck structure of the offshore platform. The jacket is a tubular steel framework that serves as a pile template and extends from the sea bed to a few feet above the wate level. Steel superstructure of the platform including decks are connected to the piling or the jacket to support the drilling and production facilities.
The piling consists of steel tubes which secure the platform to the sea bed and penetrates the soil up to 300 to 600 feet. The platform components such as the jacket, one or more decks, and piling, are built on land at fabrication yards as completely as possible in order to minimize the far more expensive offshore construction at the offshore site.
Conductor guides for positioning and guiding the conductors are framed at various elevations within the jacket and decks to provide support for the conductors such that the usual effects of environment such as waves, winds, current and the like can be safely withstood by the conductors and to maintain conductor alignment.
There are two kinds of conductor guide systems which have been utilized in the offshore industry. The first system, which is more common and older, consists of guides which are rigidly connected to the jacket and deck framework. The conductors are placed through these guides. The conductor guides and structural framework provide support for the conductors at various levels throughout the jacket and deck or decks. This type of system generally includes three kinds of conductor guide assemblies. The first kind are those within the horizontal frawework levels of the jacket and typically consist of vertical guides made out of steel tubes welded to the horizontal jacket tubular members. The other types are located in the upper and lower deck levels. The lower deck level guides are similar to those of the jacket except that they are rigidly connected to the deck floor beams. These guides are located in line with the jacket guides. The upper deck level assembly consists of a grid of beams bolted to the permanent upper deck beams supporting removable hatches which line up with the conductor guides in the lower deck. Access is provided to the lower deck level, which is typically the conductor termination level, by removing the hatches. While advantages of this type of system include the fact that conductor guides and framing are normally built within the jacket and deck during land fabrication, when jackets are set over existing wells, offshore construction thereof is required. Another problem is that this type of arrangement may not sufficiently withstand extreme environmental effects such as mud slides or ice movement.
The second type of arrangement, which has recently been utilized in areas of extreme environmental loading such as mud slide zones, consists of jacket conductor guides positioned inside a large diameter pile which has previously been driven through a jacket sleeve. The pile protects the conductors from environmental loading. The typical jacket conductor assembly consists of a series of horizontal guide frames connected to a central post and supported by the pile at its top. Additional guide assemblies similar to those described with respect to the first type of arrangement are provided in the decks of the platform. Because the jacket conductor guide assembly must be erected offshore after the jacket and piling are installed, it is required that the conductor guides for the deck sections be built offshore to conform to the orientation of the conductor guides in the pile.
Due to its length, the jacket assembly is built on land in several sections which are subsequently installed and welded together offshore. However, temporary beams are required for supporting the structure as it is assembled and installed at the offshore site. The handling of such beam supports on the top of the pile for large guides is time consuming and sometimes requires the use of cranes or similar equipment. As the jacket structures have become larger and larger, such beam supports have become more and more difficult to handle.
The present invention is drawn to a conductor guide assembly and method of assembling the same for a plurality of conductors for an offshore drilling or well platform. A first conductor guide means is disposed in and supported by and on the interior pile which extends through the jacket from below and sea bed to above the water level over the sea bed.
In accordance with one inventive feature, a second guide means is associated with at least one lower deck of the platform that is connected to the jacket. A plurality of passages are defined in the second guide means through which the conductors extend and are positioned with respect to the lower deck. The second guide means is temporarily connected such as by spot welding to the lower deck at the land based fabrication facility. It can thus be detached temporarily so that it can be rotated to align the passages with the plurality of conductors or at least the positions for the conductors in the interior pile. Thereafter, the second guide means is permanently connected, usually by welding, to the lower deck.
In accordance with another inventive feature, a third guide means is provided on the upper deck which also has a plurality of passages for permitting access to the plurality of conductors. The third guide means is supported by beams in the upper deck which permit limited rotation of the third guide means to align passages thereof with the passages of the second guide means.
In accordance with another inventive feature, the first guide means comprises a plurality of frame arrangements which are each equipped with removable bolt-on units that can be used to support the unfinished first guide means as sections thereof are assembled above the interior pile. The bolt-on units can then be removed to drop the first guide means, section by section, into the interior pile as additional sections are added.
Accordingly, an object of the invention is to provide a conductor guide arrangement which facilitates the positioning and guiding of conductors in an offshore platform so that the amount of construction work required at the offshore site is minimized.
A further object of the invention is to provide a method for assembling such a conductor guide arrangement.
Yet another object of the invention is to provide a method for assembling a conductor guide arrangement wherein the burdensome requirement of using temporary beams to support the structure is eliminated.
A still further object of the invention is to provide a conductor guide arrangement for offshore platforms which is simple in design, rugged in construction, and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.